> * December 2016 Istanbul car bombing / suicide bombing near a football stadium, killing 44 people

TAK != PKK, TAK claimed responsibility. 39 of those killed were police officers. Turkish military also kills civilians while targeting opposing militia groups.

> * June 2014 Istanbul bombing / killing 6 civilians

Link? Did this happen?

> March 2016 Ankara car bombing

TAK not PKK, again.

> * June 2006 Manavgat

Yet again, TAK.

> https://en.wikipedia.org/wiki/October_2016_Istanbul_bombing

Not intentional targeting civilians, accidental premature explosion of bomb. Only one of the attacks you've mentioned that was by the actual PKK and actually killed civilians. (e: actually no civilians killed)